AD 94-02-08

This amendment adopts a new airworthiness directive (AD) that is applicable to certain McDonnell Douglas Model MD-11 series airplanes. This action requires an inspection to detect chafing damage to certain wiring in the main avionics rack, repair or replacement of damaged wiring, and modification of the wiring installation. This amendment is prompted by a report of a chafed wire harness found on the main avionics rack on one airplane that resulted in arcing damage to the wire harness and adjacent structure. The actions specified in this AD are intended to prevent chafing of the main avionics rack wiring, which could result in arcing and a fire in the wire bundle; this could lead to damage to aircraft systems and loss of associated aircraft functions.

Final rule; request for comments.

94-02-08 McDONNELL DOUGLAS: Amendment 39-8806. Docket 93-NM-231-AD. \n\n\tApplicability: Model MD-11 series airplanes; manufacturer's fuselage numbers 447 through 558, inclusive; certificated in any category. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent chafing of the main avionics rack wiring, which could result in arcing and a fire in the wire bundle, damage to aircraft systems, and subsequent loss of associated aircraft functions, accomplish the following: \n\n\t(a)\tWithin 30 days after the effective date of this AD, conduct a one-time detailed visual inspection to detect chafing damage to the wire harnesses located on the aft side of the main avionics rack on shelves 1 through 4, left and right sides, in accordance with McDonnell Douglas MD-11 Alert Service Bulletin A24-75, dated December 22, 1993. \n\n\t(b)\tIf no damage is detected during the inspection required by paragraph (a) of this AD, prior to further flight, modify the wiring installation in accordance with the service bulletin. \n\n\t(c)\tIf any damage is detected during the inspection required by paragraph (a) of this AD, prior to further flight, accomplish the requirements of paragraphs (c)(1), (c)(2), and (c)(3) of this AD in accordance with the service bulletin: \n\n\t\t(1)\tRepair or replace the damaged wiring; \n\n\t\t(2)\tModify the wiring installation; and \n\n\t\t(3)\tPerform a return-to-service test of the affected wiring system. \n\n\t(d)\tAn alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Los Angeles Aircraft Certification Office (ACO). Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Los Angeles ACO. \n\n\tNOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles ACO. \n\n\t(e)\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished. \n\n\t(f)\tThe inspection, repair, replacement, and modification shall be done in accordance with McDonnell Douglas MD-11 Alert Service Bulletin A24-75, dated December 22, 1993. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from McDonnell Douglas Alert Service Bulletin A24-75, dated December 22, 1993. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Los Angeles Aircraft Certification Office, FAA, Transport Airplane Directorate, 3229 East Spring Street, Long Beach, California; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\n\t(g)\tThis amendment becomes effective on February 10, 1994.

Recently, one operator of McDonnell Douglas Model MD-11 series airplanes reported one instance of the auto ground spoiler failing to arm on one airplane. Investigation revealed two wires that had burnt in half and several charred wires on shelf 3 of the aft section of the main avionics rack. These wires apparently had chafed and shorted on the screws that attach the wire bundle trough assembly to the rack. Additionally, the protective tape was worn from the attach screw heads. The operator then conducted a fleet inspection and found additional wire chafing at the same location on another airplane. The operator also found worn protective tape (exposed screw heads) at various locations on the avionics racks on other airplanes. Chafing of the wiring in the main avionics rack, if not detected and corrected in a timely manner, could result in arcing and a fire in the wire bundle; this could lead to damage to aircraft systems and the loss of associated aircraft functions.\n\n\tThe FAA has reviewed and approved McDonnell Douglas MD-11 Alert Service Bulletin A24-75, dated December 22, 1993, that describes procedures for performing a visual inspection to detect chafing damage to the wire harness located on the aft side of the main avionics rack on shelves 1 through 4. It also describes procedures for repairing or replacing damaged wiring, and modifying the wiring installation by bonding nylon sheets between the wire harnesses and the protective tape on the screw heads.\n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other Model MD-11 series airplanes of the same type design, this AD is being issued to prevent chafing of the main avionics rack wiring, which could result in arcing and fire in the wire bundle, and lead to damage to aircraft systems and the subsequent loss of associated aircraft functions. This AD requires a detailed visual inspection to detect chafing damage to the wire harnesses locatedon the aft side of the main avionics rack on shelves 1 through 4. Any damaged wiring must be replaced or repaired prior to further flight. Additionally, operators are required to modify the wiring installation by bonding nylon sheets between the wire harnesses and the protective tape on the screw heads. The actions are required to be accomplished in accordance with the service bulletin described previously.\n\n\tThis is considered interim action until final action is identified, at which time the FAA may consider additional rulemaking.\n\n\tSince a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.\n\nComments Invited\n\n\tAlthough this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.\n\n\tComments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.\n\n\tCommenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 93-NM-231-AD." The postcard will be date stamped and returned to the commenter.\n\n\tThe regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.\n\n\tThe FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."\n\nList of Subjects in 14 CFR Part 39\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.\n\nAdoption of the Amendment \n\n\tAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 14 CFR part 39 of the Federal Aviation Regulations as follows:\n\nPART 39 - AIRWORTHINESS DIRECTIVES\n\n\t1.\tThe authoritycitation for part 39 continues to read as follows:\n\nAuthority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.\n\n§ 39.13 - (Amended)\n\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: